One of the trickiest black hole concepts to grasp is also one of their most basic: Black holes don’t give off any light, so how do we still manage to “see” something that is functionally invisible? Here’s a tidy explanation of how that paradox works.

Top image: Black hole artist’s concept / NASA

It’s a fairly basic question that often comes up for people when reading about black holes. Which is why this short new video from Brian Greene on the subject is so valuable. It does an excellent job of explaining that, while the black hole itself may remain invisible, what its doing to the other objects surround it—and the light that they’re throwing off—is anything but.